For this purpose devices are known in the art where various patterns are projected onto the object to be measured. For this type of three-dimensional measuring patterns and projections with variable orientation have proven useful or necessary. For this purpose the projection is deflected for example by a wobbling mirror (DE 10 2011 101 476 A1). This device has several disadvantages and the most significant one is the following:
Since the wobbling mirror is arranged between the imaging optics of the slide projector and the object to be measured, the mirror has to be comparatively large in order not to limit the illuminated portion. This requires a large amount of installation space. Furthermore a rather complex engineering design is required due to the comparatively large mass of the mirror in order to prevent imbalances during rotation of the mirror.
The wobbling motion of the mirror does not only move the projected pattern but also the illuminated portion. The effectively useable measuring field that is illuminated in each position of the wobbling mirror by a pattern is therefore significantly smaller than the portion that is illuminated in a single position of the mirror. Therefore a large portion of the illumination power is not used for illuminating the measuring field.
In view of the short measuring times that are desirable as a matter of principle for three-dimensional measuring methods an optimum utilization of the illumination power is however very important.